1. Field of the Invention
The embodiments of the invention generally relate to e-fuse structures and methods, and more particularly to methods and structures for dual silicide e-fuses.
2. Description of the Related Art
E-fuses (electronic fuses) are used in many computerized devices, such as integrated circuits, for a number of purposes, such as array redundancy, field array programming, chip-id trimming, etc. E-fuses have many advantages compared to laser fuses, because they are scalable, less prone to collateral damage, and are field level programmable. The blowing or programming of e-fuses occurs by inducing electro-migration of silicide. After programming, the resistance of the fuse is much higher than before programming.
This electro-migration is determined by a number of factors such as: current density, resistivity, and temperature. One expression of a measure (V) of electro-migration is as follows:V˜J*R*exp(−Q/kT)/kT, where J=current density, R=film resistivity, Q=activation energy, and T=temperature.
However, as circuits progress, the programming current requirements are reduced and the power supply voltage and chip area required for programming transistors are minimized. The embodiments described below address such issues.